AK4373 Datasheet, PDF (46/98 Pages) Asahi Kasei Microsystems – Low Power Stereo DAC with HP/SPK-Amp

[AK4373]
(3) Stereo Separation Emphasis Filter (FIL3)
1) When FIL3 is set to “HPF”
fs: Sampling frequency
fc: Cut-off frequency
K: Filter gain [dB] (0dB ≥ K ≥ −10dB)
Register setting (Note 41)
FIL3: F3AS bit = “0”, F3A[13:0] bits =A, F3B[13:0] bits =B
(MSB=F3A13, F3B13; LSB=F3A0, F3B0)
1 / tan (πfc/fs)
A = 10^K/20 x
,
1 + 1 / tan (πfc/fs)
1 − 1 / tan (πfc/fs)
B=
1 + 1 / tan (πfc/fs)
Transfer function
1 − z ^−1
H(z) = A
1 + Bz ^−1
M(f) = A
Amplitude
2 − 2cos (2πf/fs)
1 + B² + 2Bcos (2πf/fs)
Phase
θ(f) = tan ^−1
(B+1)sin (2πf/fs)
1 - B + (B−1)cos (2πf/fs)
2) When FIL3 is set to “LPF”
fs: Sampling frequency
fc: Cut-off frequency
K: Filter gain [dB] (0dB ≥ K ≥ −10dB)
Register setting (Note 41)
FIL3: F3AS bit = “1”, F3A [13:0] bits =A, F3B [13:0] bits =B
(MSB=F3A13, F3B13; LSB= F3A0, F3B0)
1
A = 10^K/20 x
,
1 + 1 / tan (πfc/fs)
1 − 1 / tan (πfc/fs)
B=
1 + 1 / tan (πfc/fs)
Transfer function
1 + z ^−1
H(z) = A
1 + Bz ^−1
M(f) = A
Amplitude
2 + 2cos (2πf/fs)
1 + B² + 2Bcos (2πf/fs)
Phase
θ(f) = tan ^−1
(B−1)sin (2πf/fs)
1 + B + (B+1)cos (2πf/fs)
MS0991-E-00
- 46 -
2008/09